We wish to determine the function of genes coded in the mouse H-2 complex in immune responses. We will examine the role of Ia plus promoter cells in the proliferative response to Con A and in the response to syngeneic tumors. We will map the Ia determinants expressed on various functional lymphocyte subsets including LPS responder, LPS specific suppressor cells, as well T cells required for dependent humoral responses including macrophages. We will determine the expression of Ia antigens on macrophage and Be cell clones, and chemically characterize Ia from epidermal cells and macrophages, and determine their biochemical relationship to lymphocyte Ia. We will further examine nonresponder mice for antigen specific helper T cells. These approaches will allow us to synthesize new insights from the overlap of genetics and immunology to better understand regulation in the immune responses.